1. Field of the Invention
The field of the invention pertains to medical devices employed to deliver a media to an anatomic void and, more particularly, to medical devices and methods for delivering a media to a void within a bone structure.
2. Background of the Invention
Spinal injuries, bone diseases such as osteoporosis, vertebral hemangiomas, multiple myeloma, necorotic lesions (Kummel's Disease, Avascular Necrosis), and metastatic disease, or other conditions can cause painful collapse of vertebral bodies. Osteoporosis is a systemic, progressive and chronic disease that is usually characterized by low bone mineral density, deterioration of bony architecture, and reduced overall bone strength. Vertebral body compression fractures (VCF) are common in patients who suffer from these medical conditions, often resulting in pain, compromises to activities of daily living, and even prolonged disability.
On some occasions, VCFs may be repaired by vertebroplasty and other spinal reconstructive means. Vertebroplasty procedures have been used to treat pain and progressive deterioration associated with VCF. Most often in this vertebroplasty procedure, a bone cement, such as polymethylmethacrylate (PMMA), or other suitable biomaterial, is injected percutaneously into the bony architecture under image guidance, navigation and controls. The hardening (polymerization) of the cement media and/or the mechanical interlocking of the biomaterials within the media serve to buttress the bony vault of the vertebral body, providing both increased structural integrity and decreased pain associated with micromotion and progressive collapse of the vertebrae.
Recently, it is more common to treat weakened sites in bones by embedding artificial prosthetic material or prosthetic filler in the weakened sites of the bones or in a mechanically created void within a bone structure. The prosthetic material or prosthetic filler is typically delivered to the void in the form of a fluid media, which hardens or polymerizes after a given period.
Bone tamps (bone balloons or Kyphoplasty™), a balloon-assisted procedure for treatment of VCF or other conditions, also involves injection of a bone cement into a mechanically created bone void within a vertebral body. FIG. 1 shows a side view of three vertebrae 2, 3, and 4. Vertebrae 2 and 4 are healthy vertebrae, while vertebra 3 has a weakened site 5 due to, for examples, injury, diseases, or other causes. FIG. 2A shows a cross-sectional top view of the vertebra 3, particularly showing the weakened site 5. In the bone tamp procedure, a channel 6 is first created that leads to the target site 5. A balloon tamp is then inserted into the structurally compromised vertebral body at the weakened site 5 through the channel 6. A high-pressure balloon is inflated at the target site 5, such that target bone tissues at the target site 5 are pressed against adjacent healthy bone tissues. Some claim that expanding balloon disrupts the target bone tissue and the physiological matrix circumferentially, and directs the attendant bony debris and physiologic matrix towards the inner cortex of the vertebral body vault. As a result, a void 7 at the target site 5 is created. (FIG. 2B) The balloon tamp is then collapsed and removed, leaving the void 7 within the vertebral body of the vertebra 3. Filling it with an appropriate biomaterial media, such as a bone cement, then repairs the void 7.
The balloon tamp procedure is typically performed using multiple components. For example, U.S. Pat. No. 6,248,110 B1 describes a multiple component system for creating a channel at a vertebra using a stylus, a stylet, a guide pin, a trocar, an outer guide sheath, and a drill bit. Multiple component system may be difficult to use and may be expensive.
The use of an expandable balloon tamp to create the anatomic void 7 at the target site 5 may not be possible or the most desirable in certain clinical situations. In particular, because expandable balloon has a fixed geometry and a stretch limit, it may not be the best tool for removing bone tissues precisely or for creating a desired void that has an irregular geometry.
Also, filler material for the bone may not develop its intended strength due to a variety of factors. For example, inadequate or sub-optimal mechanical interlocking of the particles or granules within the physiologic matrices or biomaterial media may result in a weaker tissue and biomaterial construct. Also, excessive voids or void distribution within the biomaterials or bone cement media may result in a construct having inadequate strength.